MFC (Microbial Fuel Cell) converts chemical energy of organic compounds into electric energy and thus has the functions of power generation and waste treatment simultaneously. Many types of waste can be used as the fuel of MFC, including domestic wastewater, high-density organic wastewater, and human/animal excrement. Therefore, MFC can generate electric energy and effectively dispose organic waste.
Below is the principle of MFC: Organic materials are oxidized by microbes in an anaerobic anode chamber; the microbes capture electrons and transfer electrons to the anode; electrons flow through the external circuit and reach the cathode; protons pass through the exchange membrane to reach the cathode and react with oxygen there to form water; thus is formed a loop for current. China application No. 200710144804.9 and No. 200710144550.0 respectively disclosed microbial fuel cells both involving the design of electrodes and wires and the selection of catalysts. A China application No. 200610104081.5 disclosed a microbial cell device involving a filmed cathode consisting of a plate cathode and a membrane stuck with each other. However, a single microbial fuel cell is hard to output the required voltage and current at present. The required voltage and current must be achieved via assembling MFCs in series or in parallel to form an MFC stack. A China application No. 200610144991.6 disclosed a stackable air-cathode single-chamber MFC. However, the prior-art patent adopts an expensive proton-exchange membrane. Although the single-chamber MFCs are stackable, the fuel/wastewater is fed into/drained out from each cell of the cell stack separately. Therefore, the stackable air-cathode single-chamber MFC is hard to prevail.
The conventional MFC has the following disadvantages:    1. The conventional MFCs originated from PEMFC (Proton Exchange Membrane Fuel Cell) and adopt an expensive proton exchange membrane as the separator. The output power of the conventional MFC is lower than that of PEMFC by two or three orders of magnitude. The proton exchange membrane-based MFC is impractical and short of utility.    2. Oxygen needs continuously supplying to the cathode for oxygen reduction reaction. The oxygen supply process consumes more energy than the energy generated. Therefore, the conventional MFC is unable to sustain the operation by itself. In 2005, an US environmental engineering specialist Logan proposed the first air-cathode single-chamber MFC, wherein the cathode chamber is omitted, and oxygen is supplied by passive aeration, whereby is possibly achieved a positive net energy output. Although a single cell of this type can work, the cells of this type are hard to stack for amplifying output.    3. The structure and operation of the conventional MFCs are unfavorable for amplifying output.